1. Field of the Invention
The present invention relates to a method using a release film for resin-encapsulating a semiconductor device.
2. Description of the Background Art
According to a method that has been employed, a semiconductor device (chip) comprised of such an element as CPU (Central Processing Unit) for example is encapsulated with resin in the state where the semiconductor device is mounted on a substrate. With this method, a resin-encapsulated substrate having a molded resin (package) on the substrate is formed. The method generally employs transfer molding that cures resin within a mold.
The semiconductor device has to have a heatsink for dissipating, to the outside, heat generated from the semiconductor device. Therefore, it is necessary to expose a part of the semiconductor device. For a CCD (Charge Coupled Device) sensor for example, a resin encapsulation molding method for a semiconductor device is employed that partially exposes the semiconductor device for detection of light. Further, for a fingerprint detection device, a resin encapsulation molding method for a semiconductor device is employed that partially exposes the semiconductor device for finger touch.
A first example of the above-described conventional resin encapsulation molding method is disclosed in Japanese Patent Laying-Open No. 2004-119410 (see page 5 and FIGS. 1 and 2). According to the disclosed method, a press member is provided on a mold surface that contacts a part of the semiconductor device and, while the part of the semiconductor device is directly pressed by the press member, the device is encapsulated with resin. Over the press member, a coating film of an engineering plastic is formed.
A second example of the conventional resin encapsulation molding method is disclosed in Japanese Patent Laying-Open No. 2002-59453 (see page 9 and FIGS. 3 to 5). According to the disclosed method, a release film that partially covers a semiconductor device is used to resin-encapsulate the semiconductor device, not in the state where a part of the semiconductor device is in direct contact with a mold surface, but in the state where the part of the semiconductor device is covered with the release film.
The conventional resin encapsulation molding methods, however, encounter the following problems.
As for the aforementioned method of the first example, the coating film of the engineering plastic has its surface that may be uneven depending on the conditions of forming the coating film. Therefore, when the uneven surface of the coating film is brought into contact with the surface of the semiconductor device, gaps are formed between the semiconductor device and the coating film. From the gaps, resin leaks onto the surface of a part of the semiconductor device. In the end, resin flash is formed on the surface of the part of the semiconductor device. The aforementioned method of the second example improves adhesion between the release film and the semiconductor device to prevent resin flash from being formed. Thus, a considerably large clamping pressure of the mold is applied, resulting in damages to the semiconductor device such as crack and chipping.